0.1x deprecate fixes 2

[technoweenie]

Fixes some minor issues with the deprecate stuff that I found while trying to port this to the master branch.

1. Fix rubocop compliant about ===
2. Refactor DeprecatedClass.proxy_class so it can accept any version. Bonus: now that the klass_name is not built in an isolated metaclass scope, it can just use the method's origclass argument for the replacement messages, without regexes.
3. Use a shared Gem::Version instance in wrappers around deprecated methods.

[olleolleolle]

A simplified and easier to maintain solution. Evolving! Still as good, too.

[technoweenie]

@BobbyMcWho: Do you have any thoughts on these changes to the Deprecate code? I want to port it to the master branch, so I need #proxy_class to accept a ver argument.

[BobbyMcWho]

@technoweenie minor changes I propose in #1077, overall great changes you've proposed!

[technoweenie]

Thanks @BobbyMcWho. I like the nested PR trick too :)